If that Babolat is your main racquet and you're using poly, that could also be your problem. It is incredibly stiff and does not reward a spin generating stroke. A good question is, why are you interested in poly? Durability or playability? You just said you can do without it whereas I would simply demolish my wallet using something with lesser durability.

Did you say that a babolat racket with poly does not reward a spin generating stroke?